Poly(1-butene) resins are excellent in heat resistance, creep resistance, stress cracking resistance, flexibility and the like, and thus are used for pipes for hot water. The joining of a pipe for hot water made of this poly(1-butene) resin to a joint is usually carried out by the heat fusing method, but a method is desired wherein the joining is carried out using a mechanical type joint whose attachment is easy. Nowadays, as for mechanical type joints, those made of a metal such as copper or brass are used. However, metal joints used in pipings for hot water supply are corroded with chlorine contained in city water, which becomes a large problem.
As an alternative to metal joints, joints made of polyacetal having high rigidity and excellent mechanical strength have also been used. These plastic-made joints are preferred over metal-made joints.
However, polyacetal hydrolyzes when it comes into contact with water of high temperature for a long term. Therefore, there is some concern that polyacetal-made joints may result in leakage of water and in an extreme case the breakage of the joints. Because of these deficiencies, alternate plastic materials that do not have these problems are desired.
It is known that mechanical joints for pipes are required to have high rigidity and mechanical strength and further be excellent in long-term heat creep resistance, hot water resistance and chlorine water resistance. Although poly(1-butene) resins satisfy this requirement, they are flexible resins and cannot be independently used as mechanical joints. Further, they lack affinity for glass fiber and when glass fiber is added as a reinforcing material, it is difficult to give sufficient rigidity and enhance the mechanical strength.
It is also known that mechanical joints are usually prepared by injection molding, and in order to enhance productivity in injection molding it is necessary to shorten molding cycle. However, the crystallization speed of poly(1-butene) resins is slow and it takes a long time for cooling in injection molding, and thus it has been difficult to enhance productivity.